Metal-to-metal sealing system

ABSTRACT

A metal-to-metal sealing element for a wellhead assembly which includes at least first and second adjacent components and first and second generally annular sealing surfaces that are each formed on a corresponding one of the components. The sealing element comprises an annular base, an annular sealing lip which projects radially toward at least one of the first and second sealing surfaces and which comprises a seal retaining groove, a soft metal sealing insert which is disposed within the seal retaining groove and which in use engages the at least one sealing surface, and an annular intermediate portion which extends between the base and the sealing lip. The intermediate portion presses the sealing insert against the at least one sealing surface in an interference fit relationship.

This application is a divisional of U.S. patent application Ser. No.09/819,121, which was filed on Mar. 27, 2001 now U.S. Pat. No.6,561,521.

BACKGROUND OF THE INVENTION

The present invention relates generally to an annular metal-to-metalsealing system for providing a fluid and pressure tight seal between twoor more components of a wellhead assembly. More particularly, thepresent invention relates to an annular sealing assembly which includesa high strength seal carrier body to which is retained an annular sealinsert that is composed of a soft, corrosion resistant metal which issufficiently deformable by seal activating force of the seal carrierbody to conform to the surface geometry and finish of a sealing surfaceand thus establish an efficient high pressure seal therewith.

Current rigid metal sealing technologies, such as Straight Bore MetalSeals (“SBMS”), Rough Casing Metal Seals (“RCMS”), FX Bonnet gaskets,and RX, BX and AX gaskets, require higher strength alloys to providestructural integrity and sealing force. These types of seals are widelyused in gate valve bonnets, surface and subsea connectors, flow boresand generally throughout wellhead equipment. The strength requirementsof these alloys can be up to 120,000 psi yield. These seals work byplastically deforming a small area into a smooth opposing surface. Theseal contact area is generally small, and these seals are generally(with a few exceptions) not reusable. Often, due to corrosionrequirements, high strength nickel alloys are selected for these seals.These seals may be sensitive to surface finish, installation damage andgalling.

SUMMARY OF THE INVENTION

The present invention provides a high-pressure, metal-to-metal sealingsystem which employs a high strength metal seal body or carrier thatfacilitates application of spring energy or preload force to a softmetal insert carried by the seal body to accomplish high pressuremetal-to-metal sealing even under conditions of poor surface finish orirregular sealing surface geometry. The present invention hasapplication to rigid metal-to-metal seal technology including SBMSseals, RCMS seals, FX bonnet gaskets, RX, BX and AX gaskets and others.The concept of the invention involves separating the structural element(i.e., the seal body) from the sealing element (i.e., the soft metalinsert). In such sealing systems, the soft metal insert may be installedby pressing, shrinking or other retention mechanisms on the higherstrength seal body.

The higher strength seal body elastically deforms and provides a springenergy characteristic to activate the seal, plastically deforming thesoft metal insert when installed. The high strength seal body alsoconfines and protects the soft metal insert against pressure andmechanical abuse. This type of sealing system increases the contactarea, allows lower alloy materials (such as 410 stainless steel or 8630or 4130 steel) to be used for the body, prevents galling, and alsoallows the soft metal insert to be replaced, thus enabling reuse of theseal body. The soft metal insert will also accommodate wider machiningtolerances and will seal against surfaces that have defects, such asscratches. This seal design may also be tolerant to slightly oval shapedseal bores.

The sealing concept of the present invention thus represents animprovement over metal seals that simply have a soft coating on thesurface or require the soft metal to be welded to the high strengthcomponent. Coatings have limited wear/corrosion life and cannot filllarge defects in the sealing area. In addition, welding the soft metalto the high strength component adds complexity, expense, and limitsmaterial selection and may preclude reuse of the seal.

So that the manner in which the above recited features, advantages andobjects of the present invention are attained and can be understood indetail, a more particular description of the invention, brieflysummarized above, may be had by reference to the preferred embodimentthereof which is illustrated in the appended drawings. It is to be notedhowever, that the appended drawings illustrate only a typical embodimentof this invention and are therefore not to be considered limiting of itsscope, for the invention may admit to other equally effectiveembodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a fragmentary vertical section of a wellhead assembly for anoil or gas well, showing a number of uses of a metal-to-metal sealingsystem embodying the principles of the present invention;

FIG. 2 is a fragmentary section, on an enlarged scale, of ametal-to-metal sealing system according to the present inventionemployed to provide a metal-to-metal seal between a valve bonnet and avalve body, or between two line flanges or other flanged annularelements;

FIG. 3 is an enlarged fragmentary section of a metal-to-metal sealaccording to the present invention between two pipes interconnected byan external pipe coupling;

FIG. 4 is a sectional view of an annular seal body embodying theprinciples of the present invention;

FIG. 5 is a fragmentary sectional view of an end portion of the annularseal body of FIG. 4 showing an annular seal groove formed in an annularsealing projection or lip thereof and further showing a soft metalsealing element located within the annular seal groove;

FIG. 6 is a partial sectional view of an annular seal body having a softmetal sealing insert located in annular end grooves thereof andrepresenting an alternative embodiment of the present invention;

FIG. 7 is a sectional view of an annular sealing assembly representingan embodiment of the present invention and having four annular sealinglips, each being provided with an annular soft metal sealing insert;

FIG. 8 is a partial sectional view of an annular seal body having a softmetal sealing insert located in an annular groove of an annular sealinglip having a generally circular or curved cross-sectional geometry;

FIG. 9 is a partial sectional view of an annular seal body having a softmetal sealing insert located in annular sealing lip having an annularsealing face of substantially planar configuration;

FIG. 10 is a partial sectional view of an annular flexible high strengthmetal seal body having a soft metal sealing insert located in an annularinsert recess and being secured in assembly with the annular seal bodyby a retainer ring;

FIG. 11 is a partial sectional view of an annular flexible high strengthmetal seal body of generally cylindrical internal configuration andhaving a pair of soft metal sealing inserts located in annular insertgrooves within respective extremities of the annular seal body;

FIG. 12 is a partial sectional view of an annular flexible high strengthmetal seal body defining a plurality of internal annular sealingprojections, ridges or bumps each defining an annular insert recesshaving an annular soft metal sealing insert retained therein for sealingengagement with a respective annular sealing surface; and

FIG. 13 is a fragmentary sectional view of an annular flexible highstrength metal seal body having an annular internal sealing projectiondefining an annular seal recess containing an annular soft metal sealinginsert and with the sealing insert shown in sealing engagement with anannular external sealing surface of a tubular member disposed intelescoping relation with the annular metal seal body.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to the drawings and first to FIGS. 1 and 2, ametal-to-metal sealing system embodying the principles of the presentinvention is shown to be provided for sealing a number of joints of awellhead or conduit assembly. The metal-to-metal sealing systemcomprises an annular metal seal body element shown generally at 10having an annular base portion 12 which defines at least one annularsealing lip 14 projecting radially toward and establishingmetal-to-metal sealing engagement with an annular surface 18 which maybe a tapered surface as shown in FIG. 1 or a cylindrical surface asshown in FIG. 2.

As is shown in greater detail in FIG. 2, the annular metal seal body 10of the metal-to-metal sealing system has an annular soft metal sealinginsert 14 a, being supported within an insert groove of the annularsealing lip 14 and defining an annular sealing surface 14 b. The annularsealing surface 14 b may be of curved cross-sectional configuration,cylindrical cross-sectional configuration or any other suitablecross-sectional configuration without departing from the spirit andscope of the present invention. As is also shown in FIG. 2, the annularseal body of the metal-to-metal sealing system also defines one or moreflexible annular intermediate portions 16 being integral with andextending from the annular base portion 12 and having the annularsealing lip 14 with its soft metal insert 14 a projecting therefrom. Theflexible annular intermediate portions 16 provide the annular seat bodywith a spring-like characteristic, so that the flexible annularintermediate portions 16 become flexed and thus preloaded duringassembly and thus continuously urge the annular sealing lip with itssoft metal insert against an annular sealing surface to maintaininterference sealing therewith. The annular seal body 10 is adapted tobe disposed in substantially concentric relation with a member 26, suchas a tubular member of a wellhead assembly, which member defines atleast one annular sealing surface 18 against which the annular sealinginsert 14 a is pressed in an interference fit relationship when theannular seal body is in functional position. A lead-in chamfer 20 on thecylindrical metal surface or wall 18 provides a means to install theannular metal seal body 10 into its illustrated functional position andto accomplish flexing and preloading of the annular seal body 10, andparticularly its flexible annular intermediate portions 16, to ensureits spring-like forcible metal-to-metal sealing engagement with thecylindrical surface 18. The cylindrical surface 18 is designed to havean axial length that is adequate to ensure that the sealing face of thesoft metal insert is always in metal-to-metal sealing contact with theannular surface 18 regardless of relative movement therebetween inresponse to temperature fluctuations or dimensional changes responsiveto pressure. During assembly, the lead-in chamfer reacts with the softmetal seals 14 a and the annular sealing projections to cause preloadingof the intermediate sections 16 so that the intermediate sections becomeflexed for continuous application of spring force to the annular sealinglips 14 to maintain the soft metal sealing inserts of the annularsealing lips in interference sealing with the annular sealing surface 18of the member 26.

In the embodiment shown in FIG. 2, the annular seal body 10 also has acentral web portion 22 that extends radially from the base portion 12 tofit into relieved areas 24 a and 24 b in the adjacent faces 26 a and 27a of annular flanges or other such structures defining the members 26,for properly positioning the annular seal body at the joint between theadjacent faces and ensuring its retention in that location. As shown inFIG. 1, the flanges or other structures defining the adjacent faces 26 aand 27 a can be components of a casing head 30, a tubing head 32, ablock valve 34, an annulus outlets 36 or a wide variety of otherstructures where metal-to-metal sealing with internal or externalannular surfaces is desired.

As further indicated in FIG. 1, the metal-to-metal sealing system of thepresent invention also can be utilized in a wellhead as (1) an annulusseal 40 between a mandrel casing hanger 42 and the tubing head 32, (2) abushing seal 44 between an annular hanger bushing 46 and the tubing head32, (3) an annulus seal 48 for tubing hanger couplings 50 in a dualtubing string completion system, and (4) an extended neck hanger seal asshown at 52.

Since the annular sealing face of the soft metal insert of the annularsealing lip is relatively narrow, may be of rounded cross-sectionalconfiguration and is significantly softer than the cylindrical sealingsurface, i.e., from about ⅕^(th) to about ⅓^(rd) the yield stress of theelastic component of the seal, it will not cause damage to thecylindrical sealing surface against which it is pressed when the annularsealing body is in functional position with respect to the cylindricalsealing surface. This small dimensioned sealing face also permits minoraxial misalignment between the sealing element and the cooperativecylindrical surface to be accommodated, such as for example between atubing hanger and the adapter element.

Tests on wellhead equipment utilizing a metal-to-metal sealing systemhaving a soft metal sealing insert, according to the teachings of thepresent invention, have shown that the surface finish at the area ofcontact between the seal element and the cylindrical surface can be asrough as 125 microinches RMS, without jeopardizing the fluid tightnessof the seal. This advantage contrasts significantly with the highlypolished surfaces required in some other metal-to-metal sealing systems,and provides cost reduction opportunities in the manufacturing process.A seal that is an example of the described design passed both API PR2and FMC 500 cycle endurance testing. Testing was done at 5000 psibetween −75° F. and 450° F.

Additional advantages provided by the present invention include (1) thefact that the cylindrical configuration of the surface against which thesealing surface of the soft metal sealing element is pressed issubstantially easier to manufacture than surfaces of otherconfigurations, such as conical, heretofore employed in othermetal-to-metal sealing systems, and (2) no special bolting or clampingarrangements are necessary.

FIG. 3 illustrates a dual metal-to-metal seal system according to theteachings of the present invention, wherein an annular metal sealingelement, shown generally at 60, is provided with two axially spacedouter circumferential annular sealing lips 60 a and 60 b being integraltherewith and projecting radially outwardly therefrom. The sealing lips60 a and 60 b are provided for metal-to-metal sealing engagement withannular inwardly facing annular sealing surfaces 62 and 64 of pipe ends66 and 68 that are secured in assembly by an internally threaded pipecoupling 70. The internal end surfaces 62 and 64 of the pipe ends are ofcylindrical configuration and are intersected by annular internalchamfered surfaces 72 and 74 which serve as lead-in chamfers duringinstallation of the annular metal sealing element 60. The annularsealing lips 60 a and 60 b each define annular seal insert recessesreceiving annular soft metal sealing inserts 76 and 78 which projectfrom the respective seal insert recesses for sealing contact with therespective annular sealing surfaces 62 and 64. The annular metal sealingbody 60, as shown in cross-section in FIG. 3, tapers from a relativelythick and substantially rigid generally cylindrical center section 80 torespective annular end sections 81 and 82 thereof so as to defineflexible intermediate sections 84 and 86. The flexible intermediatesections are flexed radially inwardly as, during assembly, the annularsealing lips 60 a and 60 b and the soft metal inserts 76 and 78 traversethe chamfered surfaces 72 and 74 in progress to the cylindrical sealingsurfaces 62 and 64. The force of assembly being applied to the flexibleintermediate sections 84 and 86 of the annular seal body 60 causesradial flexing of the intermediate sections and thus causes the flexibleintermediate sections to become spring loaded or preloaded. This featureenables the annular sealing lips and their soft metal inserts 76 and 78to maintain interference sealing with the annular sealing surfaces 62and 64 even though the respective pipe ends may change in dimension dueto temperature changes, pressure changes, etc. Thus, the seal 60 employsa high strength, elastically deformable metal body to provide energizingforce, and soft metal sealing inserts to provide the sealing mechanism.The soft metal of the annular sealing inserts allows for much highersealing interference, and also permits effective sealing on a sealing orseating pocket surface that might have surface defects due to poorquality machining or surface damage.

Referring now to FIGS. 4 and 5, an annular sealing element embodying theprinciples of the present invention and being shown generally at 90,defines an annular body section 92 of generally cylindrical outerperipheral configuration and having intermediate flexible body sections94 and 96 integral therewith. The intermediate body sections haveannular sealing lips 98 and 100 projecting radially outwardly therefrom,and each sealing lip defines an annular seal insert groove. Annular softmetal sealing elements 102 and 104 are located within the respectiveannular seal insert grooves and project radially outwardly beyond therespective annular sealing lips 98 and 100 for sealing contact withrespective annular sealing surfaces 106 and 108 of tubular elements 110and 112. The annular seal body 92 is further provided with an annularouter peripheral web 114 which is received within an annular seallocating recess 116 that is cooperatively defined by the abutting endsof the tubular elements. The intermediate sections 94 and 96 arerendered more flexible as compared with the central section 92 by virtueof tapered end surfaces 118 and 120, thus permitting flexing and springloading of the flexible intermediate sections by reaction with theinternal surfaces of the tubular elements during assembly.

FIG. 6 illustrates a smooth bore metal seal shown generally at 122,having an annular seal body 124 defining a generally cylindrical centersection 126 and having an annular seal locating web 128. The outerperiphery of the annular seal body 124 is tapered from the central bodysection to the respective ends thereof as shown at 130 and 132, thusdefining flexible intermediate sections 134 and 136. The respectiveaxial ends of the annular seal body 122 each define annular sealing lips138 and 140, each in the form of an annular sealing lip or projectionhaving an annular sealing insert groove therein. Annular soft metalsealing inserts 142 and 144 are located within the respective annularseal insert grooves and project from the grooves, with an annularsealing portion thereof disposed for sealing engagement with an annularsealing surface of a tubular element or an annular sealing surface forwhich sealing is desired. The annular sealing lips 138 and 140 may havea curved or rounded cross-sectional configuration as shown, or in thealternative may define a more flattened annular surface in which theannular sealing insert is received. The annular sealing lips may alsohave any other suitable geometry, such as generally elliptical,triangular or rectangular, as desired, and the annular seal groove mayhave any suitable cross-sectional configuration, including generallyrectangular as shown in FIG. 5, dove tailed or other undercutconfiguration to provide for retention of the annular soft metal sealinginserts.

FIG. 7 illustrates an annular sealing element shown generally at 150,which may be referred to as an “H” seal and which is useful for sealingwith an internal cylindrical element 152 which is disposed insubstantially concentric, spaced relation within abutting tubularmembers 154 and 156. Though not necessary, the tubular members are shownto have tapered connection flanges 158 and 160 that are retained inassembly by a clamp ring 162. The annular sealing element 150 defines acentral web 164 to which is integrally connected a pair of annular sealbody members 166 and 168. The annular seal body member 166 is ofgenerally cylindrical configuration and defines annular sealing lips 170and 172 at respective axial ends thereof. The annular sealing lips eachdefine annular seal retention grooves having annular soft metal sealingelements 174 and 176 located therein for interference sealing with theouter cylindrical surface 178 of the internal cylindrical element 152.Likewise, the annular seal body member 168 is also of generallycylindrical configuration and defines annular sealing lips 180 and 182each having annular seal retainer grooves defined therein and havingannular soft metal sealing inserts 184 and 186 located within therespective seal grooves, with annular portions thereof projecting fromthe seal grooves and disposed in interference sealing engagement withthe internal annular surfaces 188 and 190 of the pipe ends 154 and 156.An annular positioning web 192 projects radially from the centralportion of the annular seal body member 168 and, in operative position,is located within an annular seal location recess that is cooperativelydefined by the joint geometry of the abutting pipe ends 154 and 156.

The annular seal body members 166 and 168 are sufficiently flexible thatthey yield or flex typically during assembly of the annular seal 150with the tubular member 152 and the pipe ends 154 and 156. Thus, when insealing assembly, the annular seal body members apply continuous springforce to maintain the annular soft metal seal elements in interferencesealing engagement with the respective annular surfaces. This featureenables the seal to maintain its effective sealing capability eventhough the annular members change in dimension due to temperature orpressure fluctuations. Also, the soft metal seal members will bedeformed by the spring force and the force of assembly and willessentially fill surface imperfections of the cylindrical surfaces andachieve effective sealing. The soft metal seal members will alsoaccommodate situations where the annular members are not of perfectlycircular configuration since the soft metal seals will yield toaccommodate such sealing surface irregularities.

In the partial sectional view of FIG. 8, an annular seal body 193 isprovided with an annular sealing lip 194 which is of rounded orsemi-circular cross-sectional configuration and projects radially fromthe annular seal body for sealing engagement with a cylindrical sealingsurface, not shown. An annular soft metal seal member 196 is locatedwithin an annular seal retainer groove defined by the annular sealinglip and projects therefrom for interference sealing engagement with thecylindrical sealing surface.

In the partial sectional view of FIG. 9, an annular seal body 198 has aflexible tapered end section 200 defined by a chamfered surface 202. Atthe axial end of the tapered flexible end section is located an annularsealing lip 204 which projects radially from the annular seal body in adirection toward an annular surface. The annular sealing lip 204 is ofgenerally rectangular cross-sectional configuration and defines agenerally cylindrical or slightly curved outer peripheral surface 206.The annular sealing lip also defines an annular seal retention groovewithin which is located an annular soft metal seal insert 208. Theannular seal retention groove may be of generally rectangularcross-sectional configuration as shown or may be of undercutcross-sectional configuration without departing from the spirit andscope of the present invention.

It should be borne in mind that the cross section of the soft metalinsert for each of the embodiments of the invention set forth herein canbe circular, elliptical, triangular, rectangular, or polygonal, and theseal grooves therefor may be of corresponding or differingcross-sectional configuration as desired. The soft metal sealing insertcan be used, for example, on the sealing radii of RCMS seals, externallyenergized metal seals, and SBMS seals. Valve seats may be replaced withsoft metal sealing inserts to minimize machining costs. Soft metalsealing inserts may also be used for ball valve seats, with no need tomatch lap the valve seat and ball to accomplish effective sealing. Thesealing system of the present invention can be used for sealing oninternal or external diameters with equal success. Also, seal designscan use multiple inserts (to increase contact area), or a single inserthaving a broad sealing surface. Existing seal designs can be modifiedefficiently and at low cost to accommodate the soft insert. Radial bumpsof conventional metal-to-metal seals can be flattened and a groove addedto simply fabrication of sealing components having soft metal sealinginserts.

The partial sectional view of FIG. 10 illustrates an annular seal bodystructure 210 having at least one tapered flexible end section 212 whichis defined by a chamfered surface 214 such as discussed above. The axialend or ends of the annular seal body define an annular seal recess 216within which is located an annular soft metal seal element 218. Aretainer ring 220, such as a snap ring, is received by the axial end ofthe annular seal body and serves to retain the soft metal sealingelement 218 within the seal recess or groove. Thus, the annular softmetal seal is readily replaceable, so that the annular seal body can bereused even under circumstances where the annular soft metal seal mighthave become damaged during assembly, disassembly, or use.

Referring now to FIG. 11, the partial sectional view illustrates anannular seal body shown generally at 222, having a central body section224 and intermediate body sections 226 and 228. Flexible axial endsections 230 and 232 of the annular seal body 222 are defined by annularchamfered surfaces 234 and 236. These flexible end sections are providedwith annular seal retention grooves having soft metal sealing elements238 and 240 retained therein. The soft metal sealing elements eachdefine annular portions thereof which project radially beyond theannular surface 242 and establish interference sealing with an annularmember. The annular surface 242 may be of cylindrical configuration andmay extend completely to the axial ends of the annular seal body 222 asshown. In this case, the only portions of the seal assembly projectingradially beyond the cylindrical surface 242, except for an annularlocator web 244, the purpose of which is explained above, are thesealing lips and portions of the soft metal sealing elements 238 and240. During assembly of the annular seal body with annular surfaces,such as abutting pipe sections, the chamfered flexible axial ends of theannular seal body can be flexed by chamfered lead-in surfaces in themanner discussed above, to provide the annular seal body with preloadedspring-like characteristics upon assembly for continuous application ofradially directed force to the annular soft metal seals to maintain themin interference sealing with the respective annular sealing surfacescontacted by the soft metal seals.

FIG. 12 indicates that an annular sealing member shown generally at 250,embodying the principles of the present invention, may be provided withmore than one or two annular soft metal sealing elements. The annularsealing member is defined by an annular seal body member 252 having acentral body section 254 which defines circular sealing projections orlips 256 and 258 each defining an annular seal retainer groove having anannular soft metal seal element 260 and 262 located therein. The annularseal body is provided with flexible axial ends 264 and 266 which aredefined by chamfered surfaces 268 and 270. These flexible axial endsalso define annular projections or sealing lips 272 and 274 which haveannular seal retention grooves containing annular soft metal sealmembers 276 and 278. Typically, the plurality of metal seal inserts ofthe annular sealing member 250 have the same internal or externaldimension, so that multiple seals can be established on a cylindricalsurface to enhance the sealing capability of the annular sealing unit.If desired, however, the intermediate seals and the axial end seals oreach of the seal inserts may be of differing dimension according to thegeometry of the surface or surfaces to be sealed. The annular sealmember 250 is especially adaptable for use as a SBMS seal, with theplurality of annular soft metal seal inserts thus enhancing the surfacecontact that is ordinarily possible when seals are used having only oneor two soft metal seal inserts.

As shown in FIG. 13, sealing according to the teachings of the presentinvention may be accomplished between telescopically arranged tubularelements. A tubular element 280 having a cylindrical external surface282 is shown to be telescopically received within a tubular member 284.To accomplish sealing, the outer tubular member defines an internalannular sealing projection or lip 286 having an annular seal retentiongroove 288. An annular soft metal seal is retained within the annularseal retention groove, with an annular portion thereof projectingradially beyond the annular sealing projection 286 and thus disposed forsealing engagement with the outer cylindrical surface 282 of the tubularelement 280. It should be borne in mind that the annular sealing lipmay, in the alternative, be located at the outer periphery of the innertubular element, causing the soft metal seal to be positioned forsealing engagement with the inner cylindrical surface of an outertubular member.

As will be readily apparent to those skilled in the art, the presentinvention may easily be produced in other specific forms withoutdeparting from its spirit or essential characteristics. The presentembodiment is, therefore, to be considered as merely illustrative andnot restrictive, the scope of the invention being indicated by theclaims rather than the foregoing description, and all changes which comewithin the meaning and range of equivalence of the claims are thereforeintended to be embraced therein.

1. In combination with a wellhead assembly which includes at least firstand second adjacent components and first and second generally annularsealing surfaces that are each formed on a corresponding one of thecomponents, a metal-to-metal sealing element comprising: an annularbase; an annular sealing lip which projects radially toward at least oneof the first and second sealing surfaces and which comprises a sealretaining groove; a soft metal sealing insert which is disposed withinthe seal retaining groove and which in use engages the at least onesealing surface; and an annular intermediate portion which extendsbetween the base and the sealing lip; wherein the intermediate portionpresses the sealing insert against the at least one sealing surface inan interference fit relationship.
 2. A wellhead assembly according toclaim 1, wherein at least one of the first and second componentsincludes a frusto-conical surface intersecting the sealing surface, andwherein the frusto-conical surface functions as a lead-in chamfer forinstallation of the sealing element.
 3. A wellhead assembly according toclaim 1, wherein the sealing element comprises a plurality of sealinglips, each of which is connected to the base by a correspondingintermediate portion and each of which includes a seal retaining groovewithin which a soft metal sealing insert is disposed for metal-to-metalsealing engagement with at least one of the first and second sealingsurfaces.
 4. A wellhead assembly according to claim 3, wherein thesealing element comprises two sealing lips, each of which is positionedopposite a corresponding one of the first and second sealing surfaces.5. A wellhead assembly according to claim 4, wherein the sealing elementfurther comprises a web portion intermediate the sealing lips to locateand retain said sealing element in functional position with respect tothe first and second sealing surfaces.
 6. A wellhead assembly accordingto claim 3, wherein the first and second components are arrangedconcentrically relative to each other and wherein the sealing elementcomprises a generally U-shaped cross-sectional configuration and innerand outer sealing lips, each of which includes a seal retaining groovewithin which a soft metal sealing insert is disposed for metal-to-metalsealing engagement with the first and second sealing surfaces.
 7. Awellhead assembly according to claim 3, wherein the first and secondcomponents are arranged coaxially relative to each other and wherein thesealing element comprises a generally step-shaped cross-sectionalconfiguration and inner and outer sealing lips, each of which includes aseal retaining groove within which a soft metal sealing insert isdisposed for metal-to-metal sealing engagement with the first and secondsealing surfaces.
 8. A wellhead assembly according to claim 3, furthercomprising a third component which includes a corresponding thirdsealing surface, and wherein the sealing element comprises a generallyH-shaped cross-sectional configuration and at least three sealing lips,each of which includes a seal retaining groove within which a soft metalsealing insert is disposed for metal-to-metal sealing engagement withthe first, second and third sealing surfaces.
 9. A wellhead assemblyaccording to claim 8, further comprising a fourth component whichincludes a corresponding fourth sealing surface, and wherein the sealingelement comprises four sealing lips, each of which includes a sealretaining groove within which a soft metal sealing insert is disposedfor metal-to-metal sealing engagement with the first and second sealingsurfaces.